The invention relates to electro-optical signal processing systems.
In many signal-processing systems, charge carriers such as electrons or holes carry signal information. However, the speed of such charge carriers and the bandwidth of information carried by them is fundamentally limited by thermally induced scattering of the charge carriers in the charge transport material. In most conductors, the bandwidth of the electrical signals carried by the charge carriers is typically limited to on the order of 1-10 GHz at room temperature. Furthermore, although superconducting sources operating at liquid helium temperatures can generate electrical signals having signal bits on the order of 1 psec (a bandwidth of 1 THz), as these signals propagate the charge carriers will incoherently scatter, and the high bandwidth information will be lost.
In contrast, optical signals propagate at much faster speeds and undergo much less thermal scattering than those of charge carriers, even in optically dense materials. Moreover, generating high-bandwidth optical signals is becoming routine. For example, commercially available titanium sapphire lasers can generate pulses having durations approaching 10 fsec (corresponding to a bandwidth of 100 THz) and such pulses have been converted into pulse trains with repetition rates of 10 THz using femtosecond pulse-shaping techniques.